1. Field of the Invention
The present invention relates to a robotically controlled medical instrument.
2. Background Information
Historically, surgery has been performed by making large incisions in a patient to provide access to the surgical site. There has been developed endoscopic instruments that allow a surgeon to perform a procedure through small incisions in the patient. The instruments include an endoscope which has a camera that allows the surgeon to view the internal organs of the patient. Such procedures are less traumatic to the patient and have shorter recovery times than conventional surgical procedures. Endoscopic instruments have even been used to perform minimally invasive heart surgery.
Blockage of a coronary artery may deprive the heart of blood and oxygen required to sustain life. The blockage may be removed with medication or by an angioplasty. For severe blockage, a coronary artery bypass graft (CABG) is performed to bypass the blocked area of the artery. CABG procedures are typically performed by splitting the sternum and pulling open the chest cavity to provide access to the heart. An incision is made in the artery adjacent to the blocked area. The internal mammary artery is then severed and attached to the artery at the point of incision. The internal mammary artery bypasses the blocked area of the artery to again provide a full flow of blood to the heart. Splitting the sternum and opening the chest cavity can create a tremendous trauma to the patient. Additionally, the cracked sternum prolongs the recovery period of the patient.
Computer Motion of Goleta, Calif. provides a system under the trademark ZEUS that allows a surgeon to perform minimally invasive surgery, including CABG procedures. The procedure is performed with instruments that are inserted through small incisions in the patient's chest. The instruments are controlled by robotic arms. Movement of the robotic arms and actuation of instrument end effectors are controlled by the surgeon through a pair of handles and a foot pedal that are coupled to an electronic controller.
It is generally desirable to maximize the degrees of freedom while minimizing the size of the instrument inserted into the patient. Multiple degrees of freedom improve the dexterity of the system. Small compact instruments minimize the size of the incision in the patient.
U.S. Pat. No. 6,296,635 issued to Smith et al. discloses a medical instrument that has a number of different degrees of freedom. The instrument is moved and actuated by a series of cables and pulleys. Cable/pulley systems are relatively bulky and not conducive to small compact packaging.